In order to enable communication between various devices in substation automation or distribution automation systems there has evolved a standard that enables communication between various devices of various device suppliers. This standard is IEC 61850. According to this standard software elements of equipment are hierarchically organized in a number of levels including a logical device level, a logical node level, a data object level and a data attribute level. A logical device here normally corresponds to a device in such a system, while a logical node corresponds to a function of the device, which data objects and data attributes relate to data of such a function. There may here be several logical nodes in a logical device for a number of various functions.
One type of device used in such systems is the intelligent electronic device (IED), which is used for monitoring and/or controlling other pieces of equipment in such systems, for instance equipment like circuit breakers and transformers. In order to perform this monitoring and control there are provided I/O (input/output) connections on the IED leading to such pieces of equipment. An intelligent electronic device can include a number of functions, where there may exist one logical node for each such function being implemented by the intelligent electronic device. In the above-mentioned standard there may for instance exist ninety-two different logical nodes together with the possibility to extensions.
Some logical nodes, like for instance CSWI, which is related to SWitch Control and Indication, has optional external data objects that need extra I/O connections if used.
Pieces of equipment connected to the I/O connections of an intelligent electronic device may furthermore vary depending on the environment in which the intelligent electronic device is provided.
Also the type of communication that an intelligent electronic device is to perform with other devices on a higher or the same level in the system may vary depending on the environment.
Finally there may in some instances be needed a variation of voltage levels used for operating an intelligent electronic device.
Some of these requirements could be met more easily if an intelligent electronic device were provided with modularized hardware, i.e. that an intelligent electronic device is provided with various separable and replaceable hardware modules that provide the functionality of the intelligent electronic device.
One way of providing modularized hardware for an intelligent electronic device is described in U.S. Pat. No. 7,191,076. Here there is an intelligent electronic device having a base module to which external function modules can be attached. These external function modules offer expandable features such as additional power management, additional communications, advanced communications, wireless communications, analog and digital input/output, data logging etc.
In view of what has been described above there would therefore be of interest to provide a modular IED, both regarding hardware and software, that can be combined with a data communication standard, like IEC 61850, in order to provide flexibility regarding both the software elements provided according to the communication standard and hardware modules for allowing a free combination of both software elements and hardware modules while at the same time providing communication according to the communication standard.